Hydraulic power system



Aug 5, 1958 J. K; DOUGLAS 2,845,778

HYDRAULIC POWER SYSTEM Filed Nov. 2l, 1955 2 Sheets-Sheet 1 www ATTORNEY Aug' 5, 1958 J. K. DOUGLAS 2,845,778

l HYDRAULIC POWER SYSTEM Filed Nov. 21, 1955 2 Sheets-Sheet 2 INVENTOR JAMES K. DOUGLAS BYMW ATTOR EY United States Patent O HYDRAULIC POWER SYSTEM James K. Douglas, Shorewood, Wis., assignor to The OilgearCompany, Milwaukee, Wis., a corporation of Wisconslu Application November 21, 1955, Serial No. 547,980-

9 Claims. (Cl. till-52) This invention relates to hydraulic power systems of the type in which one or more hydraulic motors are employed to move a load and are energized by motive liquid supplied thereto by two or more pumps either selectively or simultaneously.

A power system embodying the invention is particularly adapted for steering a ship and the invention will be explained as being used for that purpose but it is to be understood that the invention is not limited to that particular use.

It is common practice to provide hydraulic motor means comprising one or more hydraulic motors for rotating the rudder stock of a ship and to connect the motor .means to two electrically driven power pumps through valve means which may be operated to isolate either pump so that the motor means is energized by one pump and the other pump functions as a standby. There is also provided a manually operated pump which is used only when both power pumps fail to operate and which normally is isolated from the steering system by manually operated valves.

In case the active power pump should become 'disabled for any reason, such as failure of the electric motor which drives it, failure of some part of the pump, or the pump running dry for any reason such as its reservoir being broken, it is necessary to transmit from the steering wheel station to the steering engine room instructions to cut the disabled pump out of the system and to cut the standby pump into the system, it being necessary to cut the disabled pump out of the system as otherwise the other pump might be bypassed through the disabled pump.

If the active pump should become disabled when the ship is near another ship or some other obstruction such as a pier, a collision may occur before the changeover of pumps can be effected. This has happened in the past with the result of heavy damage.

The present invention has as an object to provide a power system in which one pump can be cut out of the system and another pump cut into the system almost instantly.

Another object is to provide a power system including a plurality of pumps and means for automatically cutting a pump out of the system in response to that pump becoming disabled.

Another object is to provide a power system including a plurality of pumps and means for automatically cutting a pump into the system in response to that pump being started.

Other objects and advantages will appear from the following description of the embodiment of the invention illustrated schematically in the accompanying drawings in which the views are as follows:

Fig. l is a diagram of the hydraulic circuit-of a power system in which the invention is embodied.

Fig. 2 is a view illustrating on a larger scale a part of the control for one of the pumps shown in Fig. l.

Fig. 3 is a central Vertical section through one of the normally closed valves shown in Fig. 1.

q 2,845,778 Patented Aug. 5, 1958 The power system has been shown as including hydraulic motor means comprising two opposed stationary cylinders 1 and 2, two opposed stationary cylinders 3 and 4, a ram 5 which has its end portions fitted in cylinders 1 and 2 and a ram 6 which has its end portions fitted in cylinders 3 and 4. Rams 5 and 6 have blocks 7 pivoted thereto by means of pins 8 and fitted in slots 9 formed in a crosshead 10 which is fixed to the rudder stock 11 of a ship. The motor means, crosshead and rudder stock have not been illustrated in detail because the arrangement shown is well known and in extensive commercial use. lt is deemed Asuiiicient to state that, when motive liquid is supplied to cylinders 1 and 4, rams 5 and 6 will rotate rudder stockv 11 in a clockwise 'direction and, when motive liquid is supplied to cylinders'Z and 3, rams 5 and 6 will rotate rudder stock 11 in a counterclockwise direction.

Liquid for energizing motor means 1-6 is supplied by either or both of two reversible pumps P1 and P1a having, as indicated in dotted lines in Fig. l, drive shafts 14 and 14a, respectively, to which electric motors (not shown) are connected to drive the pumps. Pump P1 is adapted to discharge liquid through one and to have liquid return to it through the other of two normally closed valves V1 and V2 which will presently be described and which are fastened to the pump casing and communicate with the inlet and outlet ports of the pump. Two valves V1*L and V2a are similarly connected to pump P194. Valves V1 and V1 are connected to each other by a chan nel 15 which is connected to cylinders 1 and 4 by a channel 16. Valves V2 and V2a are connected to each other by a channel 17 which is connected to cylinders 2 and 3 by a channel 18.

Pumps P1 and P1a have not Ibeen illustrated in detail because such pumps and the pump controls have been in extensive commercial use for many years. A pump of the same general type is shown in Patent No. 2,074,- 068 and a pump control of the same general type is shown in Patent No. 2,499,633.

It is deemed sufficient to state herein that pump P1 has its pumping mechanism arranged within a casing 19 which in the present instance is mounted upon a reservoir 20 containing a supply of liquid, that casing 19 encloses a displacement varying member or slide block 21 which is movable transversely therein in a horizontal plane but is restrained from movement in any other direction, and that the pump will discharge liquid in a direction and at a rate determined by the direction and distance slide block 21 is offset from its central or zero displacement position.

The control for pump P1 includes a piston 22 which engages the left side of slide block 21 and is fitted in a cylinder 23 which is carried iby casing 19 and is continuously supplied with liquid at a low pressure as will presently be explained so that slide block 21 is continuously urged towards the right by servo-motor 22-23. The right side of slide block 21 is engaged by a piston 24 iitted in a cylinder 25' which is carried by casing 19 and has its outer end closed by a head 26. Piston 24 has a pressure area twice that of piston 22 so that slide block 21 will be moved toward the left when cylinders 23 and 25 are supplied with liquid at the same pressure.

` As shown in Fig. 2, ow of liquid into and out of cylinder 2 5 is controlled by a rotary valve 27 which has an operating lever 28 ixed upon its outer end and which is fitted in a Ibore 29 formed in piston 24 and in cylinder head 26. Valve 27 has two diagonal grooves 30 and 31 formed in its peripheral surface at opposite sides of a port 32 which extends through the wall of the hub of piston 24 and is of such size that its opposite edges align with the adjacent edges of grooves 3,0 and 31. One end of groove 30 extends to the end of valve 27 andcommunicates with the inner end of bore 29 which has a hole 33 extending through the wall thereof so that groove 30 is at all times open to drain. Groove 31 communicates with one end of a passage 34 which is formed within' valve 27 and has its other end communicating with an annular groove or port 35 which is formed in cylinder head 26 around valve 27.

Liquid for energizing servo-motors 22-23 and 24-26 is supplied by an auxiliary pump P2, indicated as being a gear pump, which has been shown separate from pump P1 in Fig. 2 in order to simplify the disclosure. Actually, however, pump P2 is arranged within casing 19 and has its driven gear fixed on drive shaft 14, as indicated in dotted lines in Fig. 1, so that pump P2 is driven in unison with pump P1 which is according to common practice.

Pump P2 when driven will draw liquid from reservoir 20 through a suction channel 36 and will discharge it into a branched supply channel 37 one branch of which is connected to cylinder 23 and another branch of which is connected to port 35 in the head 26 of cylinder 25. The liquid discharged 'by pump P2 in excess of requirements is exhausted through a relief valve 38 which enables pump P2 to maintain a constant low pressure in supply channel 37, cylinder 23 and port 35.

The arrangement is such that moving lever 28 rearward in respect to the drawing will open groove 31 to port 32. If pumps P1 and P2 are running, liquid discharged by pump P2 will llow through channel 37 and open valves V1 and V2, as will presently be explained, and it will tlow from channel 37 through port 35, passage 34, groove 31 and port 32 into cylinder 25 and cause piston 24 to move slide block 21 toward the left. Movement of slide `block 21 toward the left from its neutral position will cause pump P1 to discharge liquid through valve V1 into channel 15 and to have liquid returned to it through channel 17 and valve V2. Port 32 will move along valve 27 so that, when slide block 21 has moved a linear distance proportional to the angular distance through which lever 28 was rotated, port 32 will move out of communication with groove 31 and further movement of slide block 21 will cease.

Conversely, moving lever 28 forward in respect to the drawing will open groove 3i) to port 32. If pumps P1 and P2 are running, the liquid continuously supplied by pump P2 to cylinder 23 will cause piston 21 to move slide block 21 toward the right and cause piston 24 to expel liquid from cylinder 25 through port 32, groove 30, bore 29 and hole 33 to exhaust. Movement of slide block 21 toward the right from its neutral position will cause pump P1 to discharge liquid through valve V2 into channel 17 and to have liquid return to it through channel and valve V1. Port 32 will move along valve 27 so that, when slide block 21 has moved a linear distance proportional to the angular distance through which lever 2S was rotated, port 32 will move out of communication with groove 30 and further movement of slide block 21 will cease.

However, if pumps P1 and P2 were not running, turning lever 28 would have no effect because there would be no motive liquid to operate servo-motors 2.2--23 and 24-26.

Pumps P1 and Pa and the controls therefor are identical. Therefore, like parts have been indicated by like reference numerals with the exponent a added to the reference numerals applied to pump P1a and its controls so that further description thereof is unnecessary. However, the controls are reversed in respect to each other. That is servo-motors 24`26 and 24a-26n are arranged on the adjacent ends of the pumps and servomotors 22-23 and 2223a are arranged on the far ends of the pumps. The control for one pump is reversed in respect to the control for the other pump so that slide blocks 21 and 21EL will move in the same 4 direction in response to rotation of control levers 28 and 289' in the same direction.

More specically, moving lever 25a rearward in respect to the drawing will make the same connections as are made by moving lever 28 forward. That is, cylinder 25a will be connected to exhaust so that, if pumps P1a and P2a are running, piston 22a will move slide block 21a toward the left and piston 24a will expel liquid from cylinder- 25a. Moving slide block 21a toward the left from its neutral position will cause pump l10 to discharge liquid through valve V1a into channel 15 and to have liquid return to it through channel 17 and valve V23.

Conversely, moving lever 28EL forward inA respect to the drawing will make the same connections as are made by moving lever 28 rearward. That is, if pumps F1a and P2a are running, liquid will be supplied to cylinder 25a and will cause piston 24a to move slide block 21a toward the right. Moving slide block 21a toward the right from its neutral position will cause pump P1 to discharge liquid through valve V2a 'into channel 17 and to have liquid return to it through channel 15 and valve Vla.

Liquid discharged by the driven pump or pumps PFl and P1 into channel 15 `flows therefrom through channel 16 into cylinders 1 and 4 and causes rams 5 and 6 to rotate crosshead 1t) and rudder stock 11 in a clockwise direction and rams 5 and 6 to expel liquid from cylinders 2 and 3 through channels 1'8 and 17 to the driven pump or pumps. Liquid discharged by the driven pump or pumps P1 and P1a into channel 17 flows therefrom through channel 18 into cylinders 2 and 3 and causes rams 5 `and 6 to rotate crosshead 10 and rudder stock 11 in a counter-clockwise direction and rams 5 and 6 to expel liquid from cylinders 1 and 4 through channels 16 and 15 to the driven pump or pumps.

Control levers 28 and 28a preferably are arranged close together so that both may conveniently be connected to a steering linkage which 'has not been illustrated since it does not per se form a part of the invention and is of a type that is old and well known. 1It is deemed :suicient to state that the steering linkage is also connected to the steering wheel of the ship and to the rudder stock, that it includes follow-up mechanism, that it is so constructed that rotation of the steering wheel in a given direction will cause levers 23 and 28a to be rotated in a given direction and the resultant rotation of rudder stock 11 will cause levers 28 and 28a to be returned to their neutral positions when rudder stock 11 has been rotated through an angular distance proportional to the angular distance through which the steering wheel was rotated.

Valves V1, V2, Vla and lV2a are identical and a description of one will sutce for all. As shown in Fig. 3, valve V1 includes a valve body 40 which 'is square in cross-section and has a central axia'l bore 41 extending into it from its upper end and a transverse bore 42 extending outward from bore 41, a cylinder 43 which is bolted to the lower end of body 1 and has a branch of channel 37 connected thereto, and a pipe llange 44 which is bolted to the upper end of body 40 and has channel 15 xed thereto in communication with bore 41. Body 40 is bolted to the casing 19 of pump P1 with bore 42 in communication with one of the ports of pump P1 which has been indicated bythe reference numeral 45.

Bore 41 has closely fitted therein a valve guide 46 the upper end of which constitutes a valve seat 47 for a poppet type valve 48 having a stem 49 which extends through and is guided by the lower part of guide 16. Valve stem-49 is xed to a piston 50 which is closely tted in cylinder 43 and urged downward by la nest of springs 51. Valve seat 47 and va'lve 48 are very hard, valve seat 47 has va sharp edge and springs 51 will cause valve seat 47 to cut through any foreign matter that may lodge thereon, thereby insuring -that -there will be no leakage through the valve when it is closed. -In order to provide for exhaust of any liquidwhich may leak past piston 50 or through the t :between piston rod 49 and valve guide 46, the space between piston 50 and valve guide 4'6 communicates with a passage S2 which is connected by la pipe 53 to the interior of pump casing 19 as indicated in Fig. 1. Valves V2, V1a and V2EL are similarly connected to drain.

The arrangement is such that, when pump P1 is started, pump P2 will start to discharge liquid which will flow through channel Y37 to valves V1 and V2 and open them so that, when slide block 21 is shifted from its zero displacement position, pump P1 will discharge liquid through one and have liquid return to it through the other of valves V1 and V2. Then when pump P1 is stopped, pump P2 will Istop with it which will permit valves V1 and V2 to be closed by their springs 51 which will move pistons 50 downward and cause them to eject liquid from cylinders 43 through the idle pump P2. Likewise, valves V1f=L and V2.B4 are similarly opened in response to starting pump P1a and are closed in response to pump Pla being stopped. Either of the power pumps is thu-s automatically connected into or isolated from the steering circuit by merely starting or stopping the pump.

The electric motors which drive pumps P1 and P1a may be controlled `by switches arranged close to the steering wheel so that, if anything happens to the pump which at that time is running, a changeover of pumps may be eected merely by opening one switch and closing another switch to de-energize the motor which is driving the disabled pump and cause the other motor to start driving the standby pump. Also, the second pump can be placed in service -by merely closing a switch whenever it is desired to move the rudder stock `at high speeds in order to prevent the ship from colliding with another ship or other obstruction. Consequently, the time required to cut one pump out of service and to place the standby pump into service is reduced to a few seconds from the considerable period of time previously required.

The power system described herein may be modified in various ways and adapted to other uses without departing from the scope of the invention which is hereby claimed as follows:

l. A power system comprising hydraulic motor means, two power pumps connected to said motor means to energize the same, an auxiliary pump driven in unison with each power pump and forming therewith a pumping unit, a control connected to each power pump to control the flow of liquid therefrom to said motor means, a single valve connected between the outlet of the power pump of each unit and said motor means and being normally closed to prevent ow of liquid through said outlet, a hydraulic:

servo-motor connected to said valve, and means connecting said servo-motor directly to the auxiliary pump of that unit to enable said servo-motor to open said valve in response to said auxiliary pump starting to discharge liquid.

2. A power system according to claim 1 in which said normally closed valve is a poppet type valve, said servomotor includes a cylinder which is much larger than said valve and a piston which is tted in said cylinder and connected to said valve, and said valve is urged toward its seat by spring means which engages said piston.

3. A power system comprising hydraulic motor means provided with interchangeable inlet and outlet ports, two power pumps, fluid channels connecting said motor ports to opposite sides of each of said power pumps, an auxiliary pump driven in unison with each power pump and forming therewith a pumping unit, a control connected to each power pump for directing liquid therefrom to said motor ports selectively and for cutting off flow of liquid to said motor means, a single valve connected between each side of the power pump of each unit and said motor means and being normally closed to prevent ow of liquid into or out of said power pump, a hydraulic servo-motorv connected to said valve, and means connecting said servomotor directly to the auxiliary pump of that unit to enable said servo-motor to open said valve in response to said auxiliary pump starting to discharge liquid.

4. A power system comprising hydraulic motor means, two power pumps connected to said motor means to energize the same and each having means for varying its displacement, an auxiliary pump driven in unison with each power pump and forming therewith a pumping unit, each of said units having means connecting said displacement varying means of the power pump thereof -directly to the auxiliary pump thereof including a -control operable to direct liquid to and from the displacement varying means of the power pump thereof, a single valve connected between the outlet of the power pump of each unit and said motor means and being normally closed to prevent flow of liquid through said outlet, a hydraulic servo-motor connected to said valve, `and means connecting said servomotor directly to the auxiliary pump of that unit to enable said servo-motor to open said valve in response to said :auxiliary pump starting to discharge liquid.

5. A power system comprising hydraulic motor means provided with interchangeable inlet and outlet ports, two power pumps each having means for varying its displacement and for reversing the direction of pump discharge, fluid channels connecting said motor ports to opposite sides of each of said power pumps, an auxiliary pump driven in unison with each power pump and forming therewith a pumping unit, each of said units having means connecting said Idisplacement varying means of the power pump thereof directly to the auxiliary pump thereof including a control operable to direct liquid to and from the displacement varying means of the power pump thereof, a single valve connected between each side of the power pump of each unit and said motor means and *being normally closed to prevent flow of liquid into or out of sai-d power pump, a hydraulic .servo-motor connected to said valve, and means connecting said servo-motor directly to the auxiliary pump of that unit to enable said servo-motor to open said valve in response to said auxiliary pump start ing to discharge liquid.

6. A power system according to claim 5 in which said normally closed valve is a poppet type valve, said servomotor includes a cylinder which is much larger than said valve and a piston which is fitted in said cylinder and connected to said valve, and said valve is urged toward its seat by spring means which engages said piston.

7. A power system, for rotating the rudder stock of a ship, 'comprising hydraulic motor means for connection to said stock to rotate the same and having interchangeable inlet and outlet ports, two power pumps each having two ports for the ow of liquid thereto and therefrom and means for varying its displacement and reversing it, a normally closed valve connected to each of said pump ports, fluid channels connecting said motor ports tothe ports of both of said power pumps through said valves, an auxiliary pump driven in unison with each power pump and forming therewith a pumping unit, each of said units having means connecting said displacement varying means of the power pump thereof directly to the auxiliary pump thereof including a control operable to direct liquid to and from the displacement varying means of the power pump thereof, a hydraulic servo-motor connected to each of said valves, and means connecting the servo-motors for the valves of each unit directly to the auxiliary pump of that unit to enable those servo-motors to open the valves connected thereto whenever that auxiliary pump is discharging liquid.

8. A power system according to claim 7 in which said normally closed valve is a poppet type valve, said servomotor includes a cylinder which is much larger than said valve and a piston which is fitted in said cylinder and connected to said valve, and said valve is urged toward its seat by spring means which engages said piston.

9. A power system comprising hydraulic motor means, a. power pump operatively connected to said motor means, a standby pump, means operatively connecting said standby pump to said motor means, an auxiliary pump driven in unison with said power pump and forming therewith a pumping unit, a control connected to said power pump-to control the fiow of liquid therefrom to said motor means, a single valve connected between each port of said power pump and said motor means, a hydraulic servo motor connected to each of said valves, and means connecting said servo motors directly tothe output of said auxiliary pump to cause said servomotors i standby pump when said auxiliary pump is not discharging liquid.

References Cited in the le of this patent UNITED STATES PATENTS 1,955,922 Lamond Apr. 24, 1934 2,426,374 Sprake Aug. 26, 1947 2,499,633 Douglas Mar. 7, 1950 

